Ramp with feedback,
not a magic curve.

A schedule is a hypothesis with stop conditions.

Warmup is a controlled increase in wanted, authenticated email while receivers learn the behavior of a changed IP or domain. The curve is only an initial operating plan. SMTP responses, complaints, bounces, authentication, and provider reputation data decide whether the next increase is justified.

New IP, new domain, and migration are different changes.

A dedicated IP needs its own sending history. A new domain can be unfamiliar even on provider-managed shared infrastructure. A migration can preserve domain reputation while changing IPs, DKIM keys, return paths, headers, and cadence. Record exactly what changed and segment that traffic instead of treating every scenario as “brand new.”

Ten thousand messages is not one reputation event.

Capacity and feedback emerge independently at Gmail, Microsoft, Yahoo, corporate gateways, and other destinations. A list that is 70% Gmail warms very differently from one that is 10% Gmail. The manifest makes the assumed split explicit so operators can compare planned and actual volumes per receiver.

Hold before a weak signal becomes a pattern.

Google tells senders to increase slowly, send at a consistent rate, begin with engaged recipients, monitor SMTP responses and Postmaster Tools, and reduce volume when bounces or deferrals rise. Its current guidance says to keep user-reported spam below 0.1% and avoid ever reaching 0.3%. Open rate is not a receiver-side control signal: Google says it does not track opens and cannot verify third-party open-rate accuracy.

Move the audience in observable cohorts.

Preserve the old path long enough to shift traffic deliberately. Start with recent, consented recipients, compare receiver-level outcomes, and avoid changing provider, From identity, content architecture, cadence, and audience policy all at once. If the new path is deferred, route only according to a documented rollback plan; uncontrolled retries can turn throttling into a volume spike.

Email warmup FAQ.